Disposable sterile apparatus for blood filtration with a system for optimizing the recovery of blood between pouches

ABSTRACT

A disposable sterile apparatus (1) for blood filtration with a system for the optimization of blood recovery in the passage from one pouch to the next, having a main tube (4, 8, 13, 18, 19) containing sterile air, one end of which is designed for the connection to a first container (pouch) (2) containing the liquid to be filtered and the other end of which is connected to a second empty container (pouch) (20): The foregoing tube (4, 8, 13, 18, 19) includes at least one filter (12) being arranged in the flow of the liquid. The apparatus (1) contains a tube (7) for the return of air from the second container (20) to the first container (2) acting to equalize pressure of the liquid at the two extremities of the main tube (4, 8, 13, 18, 19) after the liquid has been filtered. The filter (12) features two interior semi-chambers with filtration material separating them. The first semi-chamber has an inlet port while the second semi-chamber has an outlet port and a venting port. Tubing (14) allows the venting port to communicate with the end of the main tube connected to the first container (2) so that the filter may be emptied.

This application is a continuation of application Ser. No. 08/755,284filed Nov. 22, 1996, now U.S. Pat. No. 5,776,338, which is acontinuation of application Ser. No. 08/292,464 filed Aug. 18, 1994, nowabandoned.

BACKGROUND

The present invention concerns a disposable sterile apparatus for thefiltration of blood having a system for optimizing the recovery of bloodin the passage from one container (pouch) to another.

The use of pre-assembled lines, designated tube sets, for single use toassure the sterility of the assembly for the filtration of bloodcontained in one pouch to a second empty pouch is now typical in themedical equipment sector. These sets are essentially composed of a tubein plastic equipped at the ends with quick couplings for a spike and apouch that is empty of both liquid and air. At the center of the sectionof tube there is a filter designed to filter out any leukocytescontained in conserved blood and platelet concentrates, extraneousparticles, etc. During use, the set is connected to a blood container,which is normally a pouch having the same dimensions and characteristicsas the empty pouch, the container being suspended from a stand and, dueto the effects of gravity, the medicament or the blood drips into theempty pouch. At the end of the process, i.e. when the upper container isempty, the final volume of liquid or blood present in the tube set tendsto remain in the tube because of the negative pressure progressivelycreated inside the assembly; because of this phenomenon a final quantityof blood or medical liquid is effectively lost during the filtrationprocess.

Even if this negative pressure is relieved, because of thecharacteristic microporosity of the median filter element, andparticularly, because after the filtration of blood the filter elementtends to clog progressively thus reducing its degree of porosity in sucha way that free air is no longer able to enter the filter medium,complete emptying of the pouch is prevented.

In practical terms, the so-called "bubble point" of the filter, thisbeing the pressure value that the air must reach in order to passthrough the capillaries of the filtration element soaked in blood, isnot effectively reached. Therefore, the filter may not remain saturated.

To solve this problem, the Applicant has already developed a perfectedfilter, illustrated in FIG. 2, that comprises a filter body, having aninlet and an outlet, the filter being divided into at least twosemi-chambers by an internal partition of filter material and one ofthese two chambers, the semi-chamber serving for evacuation beingequipped with its own air inlet line in communication with the areaexternal to the filter body.

Notwithstanding the above, if outside air is utilized to allow thefilter to be completely evacuated, an inlet filter is required forpurification purposes. Moreover, the air cleaned by the inlet filterwill inevitably be less pure than the sterile air.

The purpose of the present invention is to eliminate the problemsmentioned above by developing a disposable sterile apparatus for thefiltration of blood with a system for optimization of the recovery offiltered blood, which serves to recover the blood remaining in thefilter in an optimized manner with respect to known apparatuses and todo this in a completely sterile ambient.

Within the framework of the foregoing purpose, one object of the presentinvention is to create an apparatus of simple design and highreliability that can be manufactured relatively easily and atcompetitive costs.

A second and equally important object is to create an apparatus with theuse of fewer elements than known devices.

SUMMARY OF THE INVENTION

The above object, in conjunction with the forgoing purposes and otherobjects that will be outlined more clearly in the following pages, areachieved by means of a disposable apparatus for blood filtration with asystem for the optimization of blood recovery, comprising a main tubecontaining sterile air, designed to be connected at one end to a firstcontainer containing the liquid to be filtered and the other end to anempty container, with said tube comprising at least one filter,characterized in that the filter has a line for the return of air fromthe second container to the first container with the purpose ofequalizing pressure of the liquid at the two ends of the tube(comprising at least one filter element) after the liquid has beenfiltered.

The characteristics and advantages of the invention will be clarified bythe description of a preferred embodiment chosen for the purposes ofillustration and shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation of an apparatus according to the presentinvention.

FIG. 2 is a cross section of a possible design of a filter utilized inthe apparatus shown in FIG. 1.

DETAILED DESCRIPTION

With reference to the above-mentioned figures, 1 indicates an apparatusaccording to the present invention. 2 indicates a first container(pouch) containing the blood to be filtered. Container 2 is connected tothe apparatus 1 by means of a spike 3 designed for insertion into anoutlet of the container 2.

The spike 3 is connected to an initial section 4 of a main tube. On theinitial section 4 of the main tube there is a tube clamp 5 for startingthe filtration. The first initial section 4 of the main tube isconnected to a three-way union 6, which connects the first initialsection 4 of the main tube to an air return tube 7 and a second initialsection 8 of the main tube. The air return tube 7 includes a check valve7a that allows the passage of air only toward the first container 2.

A second initial section 8 of the main tube is connected to a dripchamber 9a of an initial aggregate filter 9. On the second initialsection 8 of the main tube there is a safety tube clamp 10. The outletfrom filter 9 is connected to a front connector 11 of a second selectivefilter 12 by means of an intermediate section 13 of the main tube. Oneend of an filter vent tube 14 for emptying the second filter 12 isconnected to the top of the drip chamber 9a beside the second initialsection 8 of the main tube. The other end of the tube 14 is connected toa rear connector 15 of the filter 12. Inside the filter vent tube 14there is a break-off element 14a that permits the passage of liquidthrough tube 14 only when said element 14a has been fractured by theuser.

An outlet of the second filter 12 comprises an outlet connector 16located at the bottom of the second filter 12 on the side of connector15. Moreover, outlet 16 of the second filter 12 is connected to a secondthree-way union 17 by means of a final section 18 of the main tube. Onthe first final section 18 of the main tube there is an air return tubeclamp 18a. Moreover, the other end of the air return tube 7 is alsoconnected to the three-way union 17.

Finally, an empty second container (pouch) 20 is connected to the outletof union 17 by means of a second final section 19 of the main tube. Thesecond final section 19 of the main tube includes a second safety tubeclamp 19a.

It is emphasized that all the tubes in the apparatus disclosed in theinvention will initially contain only sterile air and that the device isa "closed circuit system", that is, at no point during the process doesexternal air enter the apparatus 1.

FIG. 2 shows a possible design of the selective filter 12. The filter 12is essentially composed of a body 21 on which the front inlet connector11 of the liquid to be filtered is located and also the rear connector16 for emptying of the liquid to be filtered.

The filter body 21 is divided into at least two semi-chambers 21a and21b which are, respectively, for the inlet of liquid to be filtered andthe evacuation of the liquid after filtration, and a filter medianpartition 22. The front connector 15 serves to allow air to enter theevacuation semi-chamber 21b thus making it possible for the semi-chamberto empty completely.

Operation of the apparatus 1 in accordance with the claims of thepresent invention is as follows: spike 3 is inserted into the firstcontainer 2 containing the liquid to be filtered. The filtration starttube clamp 5 is opened and the liquid to be filtered enters the first 4and second 8 section of the main tube. The inlet of liquid into the airreturn tube 7 is prevented by the check valve 7a. The liquid continuesto flow toward the first filter 9, dripping slowly into the dripchamber-9a. The inlet of liquid into tube 14 for emptying of the secondfilter 12 is prevented by the connection of said tube 14 to the top ofthe drip chamber 9a. If the drip chamber 9a should fill with liquid theinlet to tube 14 is equally prevented by the break-off element 14a.

After passing through the intermediate section 13 of the main tube theliquid enters the second selective filter 12 by way of the front inletconnector 11. The liquid passes through the filter partition 22 andfiltered liquid exits from filter 12 through the rear outlet connector16 thus filling the empty container 20 by way of the first 18 and thesecond 19 final section of the main tube.

When the first container 2 is emptied, sections 4, 8, 13, 18 and 19 ofthe main tube will remain full of liquid to be filtered because of thereduced pressure. Also filter 12 will remain full of liquid to befiltered.

Once the first container 2 is empty, the second container 20 willcontain the liquid from the first container 2 except for that liquidwhich has remained inside filter 12 and in the main tube 4, 8, 13, 18,19 and the sterile air that was initially held in the main tube 4, 8,13, 18, 19 and in the two filters 9, 12, which has been forced intosecond filtered liquid container 20.

At this point the air return tube clamp 18a must be closed and thesecond container 20 must be turned upside down and pressed therebyforcing the sterile air which it contains to flow through the air returntube 7, the check valve 7a and the first section 4 of the main tube sothat it enters the first container 2.

Once the air from the second container 20 and the blood contained in thefirst initial section 4 of the main tube has passed to the firstcontainer 2 the air return tube clamp 18a must be opened. The pressureof the air surrounding the liquid contained in the tube and in thefilters (9, 12) is now equalized and, due to the force of gravity, theliquid empties from the main tube (and container 2--the liquidpreviously contained in section 4), the first filter 9 and the firstsemi-chamber 21a of filter 12, descending toward the second container20.

At this point the break-off element 14a is fractured thereby permittingair to pass through tube 14. The air remaining in the first container 2is sufficient to empty the evacuation semi-chamber 21b of filter 12.

Since the air is free to pass through both inlet tubes 13 and 14 offilter 12, both the semi-chambers 21a and 21b of filter 12 are emptied,thereby further improving the recovery of filtered liquid.

The passage of air from one container to the other and the successiveemptying of the tubes and the filters can, if necessary, be repeatedseveral times.

It is also possible to compress the first container 2 to force theliquid transfer to the second container 20, even though this action isnot strictly necessary since the effect of gravity is sufficient torecover liquid. Compressing the first container 2 is not recommendedhowever, particularly when filtering blood, because the compression cangive rise to modification of the corpuscular part of the blood. Whilethe invention has been described by reference to one preferredembodiment chosen for the purposes of illustration, it should beunderstood that numerous changes could be made to details of the designwithout departing from the spirit and scope of the invention.

In practice, the materials used and the shapes and dimensions of theapparatuses can be varied limitlessly as required.

What is claimed is:
 1. A disposable sterile apparatus for bloodfiltration having a system for optimizing the recovery of bloodcomprising:a) a main tube, one end of the main tube being connectable toa first container for containing a liquid to be filtered and the otherend being connectable to a second container for receiving filteredliquid; b) at least one filter disposed along the main tube, the filterdefining an interior chamber, filtration material partitioning theinterior chamber into two semi-chambers, the first semi-chamber havingan inlet port for the inlet of liquid to be filtered and the secondsemi-chamber having an outlet port for the outlet of filtered liquid,the second semi-chamber further having a connector communicating withthe one end of the main tube by means of a filter vent tube; and c) anair return tube for facilitating the return of air from the secondcontainer to the first container thereby equalizing the pressure in thefirst and second containers, one end of the air return tube beingconnected to the main tube at a first connection point interposedbetween the one end of the main tube and the inlet port of the at leastone filter, the other end of the air return tube being connected to themain tube at a second connection point interposed between the outletport of the at least one filter and the other end of the main tube. 2.The apparatus of claim 1, further comprising a check valve disposed onthe air return tube for preventing the passage of fluid from the firstcontainer to the second container and for permitting the flow of airfrom the second container to the first container.
 3. The apparatus ofclaim 1, further comprising valve means for selectively stopping theflow of liquid from the main tube to the second container and preventingthe flow of air into the main tube when air is flowing from the secondcontainer to the first container, the valve means being interposedbetween the outlet port of the at least one filter and the secondconnection point.